Apparatus for determining critical temperatures



Dec. 1934- G. ALLEMAN ET AL. 1,982,620

APPARATUS FOR DETERMINING CRITICAL TEMPERATURES Filed May 15, 1932 WMAMPatented Dec. 4, 1934 UNITED STATES PATENT OFFICE APPARATUS FORDETERMINING CRITICAL TEMPERATURES poration of New Jersey Application May13, 1932, Serial No. 611,024

9 Claims.

The object of the invention is to provide an apparatus for determiningcritical temperature, that is, that temperature above which,irrespective of the pressure applied, a substance which is capable ofbeing converted into a gas cannot be liquefied. For the determination ofthe critical temperature of many substances, including stablehydrocarbons, satisfactory means are known; but such means are notreliable or practicable, if indeed they can be said to be operative, asapplied to other substances, particularly those complex mixtures ofhydrocarbons which comprise crude petroleum oil and fractions thereofsuch as fuel oil, gas oil, kerosene, heavy naphtha and gasoline.

In the determination of the critical temperatures and of the criticalpressures of compounds such as water and benzene, no specialcontrivances for rapid heating are required, because these compounds arestable and do not break down during the time required to make thedeterminations. In the determination of the critical temperatures and ofthe critical pressures of a mixture of petroleum hydrocarbons, heatingat a slow rate, through the range of temperatures under the criticaltemperature, effects cracking of the mixture; that is, many of thehydrocarbons break down to produce new hydrocarbons. These newhydrocarbons individually have critical temperatures different fromthose which are broken down to produce them. Since (it is believed) thecritical temperature of a mixture of substances is the average of thecritical temperature of the individual components (assuming equalamounts of all components), it will be understood that when a mixture ofhydrocarbons is substantially cracked, necessarily it has a criticaltemperature different from that of the mixture before cracking. Crackingis a factor of both temperature and time. If the hydrocarbon mixture isheated with sufficient rapidity through its cracking range, there willbe no substantial amount of cracking. We have found that, in the case ofgas oila typicalmineral oil fraction-not over about three minutes shouldelapse from the time it reaches a temperature of 700 F. until it reachesits critical temperature. Such slight amount of cracking as occurs inthis short period of time does not interfere with the attainment ofreasonably and sufilciently accurate results. By a. long series ofexperiments employing various petroleum hydrocarbons, it was determinedthat satisfactory and reliable results can be obtained if thedeterminations are made in a period of not over about seven minutesfourminutes of which are required for the oil to attain the temperature ofits immediate heating agent, as hereinafter described.

One difliculty, therefore, in devising a suitable critical temperaturedetermination apparatus is to provide an apparatus wherein the oil maybe heated up with sufficient rapidity through its cracking zone to avoidan amount of cracking that will substantially change its criticaltemperature.

Another difficulty is to determine what available materials are requiredthat will possess properties permitting of their use and that will, atthe same time, withstand the very high pressures produced.

- Another difiiculty is the placement of the thermometer or othertemperature recording instrument in such a way as to reliably indicatethe temperature of the oil. 75

Another difficulty is to provide means whereby the operator can make thenecessary observations. The high pressures produced often causeexplosions of the tubes containing the oil. The operator must thereforebe some distance from the .tube containing the hydrocarbon mixture andfrom the temperature indicating scale and must be protected by a shield.It is therefore necessaryto provide special means for speciallyilluminating the upper level of the liquid oil, since it is requisitethat he should closely observe the meniscus, since its suddendisappearance indicates that the critical temperature has been reached.This cannot be done without special illuminating means largelyconcentrated on the oil and the avoidance of dissemination of light bythe heating medium. This latter requirement excludes the employment ofsuch convenient and otherwise satisfactory methods of heating asincandescent electrically heated resistant wire, since the lightradiated thereby interferes with the field of vision of the operator. Wehave, however, solved this difficulty by heating the tube contain ingthe oil by the radiant heat from a dark object. We have also devisedmeans whereby light may be concentrated upon the oil at its upper levelbefore, and when, it reaches its critical temperature.

Another difficult requirement is to provide means for uniformly heatingthe entire body of oil.

All these difliculties we have overcome by long experimentation; Theinvention is capable of embodiment in different forms. The apparatusshown in the drawing is an embodiment which has been successfully usedand the accuracy of which has been demonstrated by using it to determinethe critical temperatures of stable substances whose criticaltemperatures have been repeatedly determined by other means and whichare given in various printed publications.

In the drawing:

Fig. 1 is a perspective view of the apparatus.

Fig. 2 is a plan view of the apparatus.

Fig. 3 is a perspective view of the heating element with thermometer inposition.

Fig. 4 is a view of the tube containing the material whose criticaltemperature is to be determined.

The oil whose critical temperature is to be determined is placed in atube e of barometer tubing composed of strong and well annealedboro-silica glass. The tubes may be composed of any other sufiicientlytransparent material which will withstand the high pressures incidentalto the critical temperature determination procedure.

This tube containing the oil is placed in a heating block which weconstruct as follows: A cylindrical forging is made of a material whichwill absorb and radiate heat while remaining dark or comparatively dark.A suitable material is manganese bronze. Manganese bronze will notreadily oxidize and will radiate the heat to the glass barometer tubequite rapidly. Other materials than manganese bronze may be employed,but they should be composed of alloys which will not oxidize and whichwill rapidly transfer the heat to the glass barometer tube. Acylindrical forging a of this material is made of a diameter of about 6inches and a height of about '7 inches. A hole of one inch diameter isbored through the axis of the cylinder. Holes of suitable diameter aredrilled at various places to form thermometer and tube wells. A slit orslits about one-eighth of an inch in width and intersecting the tubewell or wells and the center of the cylinder are sawed through thecylinder. To simplify the disclosure, we show in the drawing a cylinderprovided with only two wellsone awell b to receive the oilholding tube,the other a well 0 to receive the lower end of a thermometer, and adiametrical slit d intersecting the well b. The two wells must be sorelatively positioned that the temperatures therein will be the same, sothat the thermometer will accurately register the temperature of theoil. This may be rendered certain by sealing a thermocouple in abarometer tube, inserting this tube in well b, inserting the thermometerin well 0, and comparing their readings.

As an example of dimensions and locations that have proved to givesatisfactory results, the tube well may be drilled to a depth of 5inches and may be of a diameter of one-half inch. The thermometer wellmay be drilled to a depth of 3 inches and may be 11/32 inch in diameter.The wells may be drilled about one inch from the circumference of theblock and about five-eighths of an inch from each other.

The oil-holding tube e is filled with such quantity of oil that, at thecritical temperature, the meniscus will be very near the top of thetube; that is, the liquid at this temperature will nearly fill the tube.Experience has shown that the tubes filled to about one-third theirvolume, at room temperature, fulfill this condition.

Since it is necessary for the operator to observe only the meniscus andnot the entire column of oil, the slit d need be of the height requiredto expose only the upper portion of the tube to the operator's vision.

The block a is mounted upon or above any suitable heater, such as a gasstove g. The block is surrounded and covered with heat insulating orrefractory insulating material I such as a porous silica brick made fromdiatomaceous earth. This insulating enclosure may be conveniently formedin two parts which, when brought together, form an enclosure which iscomplete at sides and top except for slits i and a hole 7'. Theenclosure 1 and block a are so relatively positioned that slits i and dalign with each other and hole :i aligns with the thermometer well 0 asshown in Fig. 2.

At one side of the heating contrivance described is an adjustable microlamp is provided with a focusing condensing lens so positioned as tothrow its light rays through slits i and d and thus illuminate thecritical temperature tube at the upper part thereof. On the other sideof the described heating contrivance is a metal shield m provided with aglass window n, which is in line with the slits i and d. In front of theupper part of shield m and extending above it is a shield o of polishedwire glass.

A thermometer p is placed in the well 0 and extends through hole a to aconsiderable height above the roof of the refractory enclosure f. Theexposed part of the thermometer is housed within a glass tube 12 inorder to prevent the (relatively) cold air from contacting with thethermometer. Instead of using a thermometer, a thermocouple may beemployed, but experience has shown that accurately calibratedthermometers are more convenient than thermocouples.

After the block R: has been heated to a temperture below the criticaltemperature of the contained oil but as near to that temperature as canbe safely estimated, the tube containing the oil is placed in the well band the block is rapidly heated by means of gas flames at the bottom.This operation and subsequent observations are made in a dark room. Theoperator carefully observes the meniscus; this observation being madepossible by the special illumination of the upper end of the oil tube incontrast with the darkness of the heating block a. Immediately uponobserving the disappearance of the meniscus, he views the temperaturescale through a properly positioned vertical slot 1 in the shield m.This indicated temperature is the critical temperature of the-oiL- Thetemperature scale is illuminated by a special lamp s.

It is diflicult to determine the exact time at which the meniscusdisappears. To facilitate observation we have successfully used aspecially designed magnifying lens with a fiat field. This lens (t) maybe positioned as shown in Fig.1. We have also used a periscope andactinic spectacle glasses. We have also found that a planar objectivegreatly aidsv in making accurate observations.

The accuracy of the thermometer should be determined by calibration. Theaccuracy of the entire apparatus is proved by using it to determine thecritical temperatures of substances, such as benzene and naphthalene,whose critical temperatures have been previously determined with greatcare by other observers by means of other devices which have been foundreliable in the determination of stable substances.

What we claim and desire to protect by Letters Patent is:

1. A critical temperature determination apparatus comprising a blockprovided with a well for the reception of the substance whose criticaltemperature is to be determined, said block being of a material adaptedto absorb and radiate heat while remaining relatively dark, means toheat the block and thereby heat said substance, a protective shield forthe block, and means to illuminate and render visible the upper part ofsaid well.

2. An apparatus for determining that critical temperature of a substanceconvertible into a gas above which, irrespective of the pressureapplied, it cannot be liquefied, comprising a substantially solid blockadapted to absorb and radiate heat and transmit heat to said substanceand to the temperature indicating instrument hereinafter specified, saidblock being provided with passages of restricted dimensions into which atube containing said substance and a temperature indicating instrumentare insertable so as to occupy loci subject to the same degree of heat,means to heat the block and a. shield of heat insulating materialenclosing the block.

3. An apparatus for determining that critical temperature of a substanceconvertible into a gas above which, irrespective of the pressureapplied, it cannot be liquefied, comprising a block adapted to absorband radiate heat and transmit heat to said substance and to thetemperature indicating instrument hereinafter specified, said blockbeing provided with wells adapted to receive respectively a tubecontaining said substance and a temperature indicating instrument andprovided also with a slit through which the meniscus of said substancemay be observed, said block being otherwise substantially solid, andmeans to heat the block, said wells being so relatively positioned as toinsure the subjection, at the same time, of said substance and thetemperature indicating instrument to the same degree of heat.

4. A critical temperature determination apparatus comprising a blockprovided with a well for the reception of the substance whose criticaltemperature is to be determined, said block being of a material adaptedto absorb and radiate heat while remaining relatively dark, said blockbeing provided with a slit intersecting said well, and a lamp sopositioned that light rays therefrom pass through said slit andilluminate the substance contained therein so that its meniscus may beobserved by the operator.

5. A critical temperature determination apparatus comprising a blockprovided with a well for the reception of the substance whose criticaltemperature is to be determined, said block being of a material adaptedto absorb and radiate heat while remaining relatively dark, a shield ofheat insulating material surrounding and overlying the block, said blockand shield being provided with aligning slits, the slit in the blockintersecting said well, and a lamp so positioned that light raystherefrom pass through said slits and illuminate the substance thereinso that its meniscus may be observed by the operator.

6. A critical temperature determination apparatus comprising a blockprovided with a well for the reception of the substance whose criticaltemperature is to be determined, said block being of a material adaptedto absorb and radiate heat that its meniscus may be observed by theoperwhile remaining relatively dark, a shield of heat insulatingmaterial surrounding and overlying the block, said block and shieldbeing provided with aligning slits, the slit in the block intersectingsaidrwell, a lamp so positioned that light rays therefrom pass throughsaid slits and illuminate the substance therein, and a shield at theside of said block opposite said lamp and provided with a transparentarea in line with said slits and through which the operator may observethe illuminated meniscus of the substance contained in said well.

7. A critical temperature determination apparatus comprising a blockprovided with a well for the reception of a temperature-indicatinginstrument and a well for the reception of a tube containing thesubstance whose critical temperature is to'be determined, the blockbeing provided with a slit intersecting the second named well, means toheat the block, said block being of a material adapted to absorb andradiate heat while remaining relatively dark, and a' lamp so positionedthat light rays therefrom pass through said slit and illuminate thesubstance therein so ator.

8. A critical temperature determination apparatus comprising a blockprovided with a well for the reception of a temperature-indicatinginstrument and a well for the reception of a tube containing thesubstance whose critical temperature is to be determined, the blockbeing provided with a slit intersecting the second named well, means toheat the block, said block being of a material adapted to absorb andradiate heat while remaining relatively dark, a lamp so positioned thatlight rays therefrom pass through said slit and illuminate the substancetherein so that its meniscus may be observed by the operator, and ashield of heat insulating material extending around and above the block,said shield having slits aligning with the slit in the block and havinga hole through and above which a temperature-indicating instrumentinserted in the first named well, may extend to permit temperaturereadings.

9. A critical temperature determination apparatus comprising a blockadapted, when heated to the required temperature, to radiate heat without radiating a substantial amount of light and provided with wells, atube, adapted to contain the material whose critical temperature is tobe determined, inserted in one of said wells, a thermometer inserted inand projecting above another of said wells, the block being providedwith a slit intersecting the first named well for passage of lightthrough the block, a glass tube housing the projecting portion of thethermometer, heat insulating bricks forming a shield for the block,means to heat the block, a lamp provided with a focusing condensing lensadapted to transmit 135 light through said slit, a metal shield oppositethe lamp and provided with a transparent area in line with the slits,and means outside said'shield to receive the light rays passing throughsaid slit and transmit them to the eyes of the operator.

GELLERT ALLEMAN. AUGUSTINE FRANCIS STEPHEN MUSANTE.

